WM8941 datasheet(56/96 Pages) WOLFSON

56 / 96 page

WM8941

Pre Production

PP, Rev 3.3, December 2007

RECOMMENDED VIDEO BUFFER INITIALISATION SEQUENCE

Power Up (Video signal AC coupled to Video Buffer input):

Turn on external power supplies. Wait for supply voltages to settle.

Reset internal registers to default state (software reset).

Set VMIDSEL[1:0] bits for 50kΩ reference string impedance. *Note 1.

Enable bias (BIASEN=1) and Level Shift circuits (LVLSHIFT_EN=1).

Set Video Buffer Gain (VBGAIN) as required.

Set Video Buffer Filter Q Boost (QBOOST) as required.

Enable Video Buffer Clamp (VBCLAMPEN=1).

Enable Video Buffer Pulldown to High Impedance (VBPULLDWN=1).

Enable video buffer (VBUFEN=1).

10.

Wait for 1.5seconds.

11.

Disable Video Buffer Pulldown (VBPULLDWN=0).

Power Up (Video signal DC coupled to Video Buffer input):

Turn on external power supplies. Wait for supply voltages to settle.

Reset internal registers to default state (software reset).

Set VMIDSEL[1:0] bits for 50kΩ reference string impedance. *Note 1.

Enable bias (BIASEN=1) and Level Shift circuits (LVLSHIFT_EN=1).

Set Video Buffer Gain (VBGAIN) as required.

Set Video Buffer Filter Q Boost (QBOOST) as required.

Enable video buffer (VBUFEN=1).

Notes:

1. Choose the value of VMIDSEL bits based on the startup time (VMIDSEL = 10 for the slowest

startup, VMIDSEL = 11 for the fastest startup). Startup time is defined by the value of the

VMIDSEL bits (the reference impedance) and the external decoupling capacitor on VMID.

WM8941 датащи(PDF) 56 Page - Wolfson Microelectronics plc